The present invention relates to a fuel cell system, and in particular, to a technique for enabling a desired generation amount to be achieved even when it is difficult to provide an appropriate fuel gas supply amount for a requested gas amount such as during activation.
Efforts have been made to develop a fuel cell system comprising a fuel cell including a fuel pole and an oxidizer pole on the opposite sides of a solid polymer electrolyte membrane (hereinafter referred to as an electrolyte membrane); a fuel gas, for example, a hydrogen gas, is supplied to the fuel pole while an oxidizer gas, for example, air, is supplied to the oxidizer pole so that the fuel cell can generate electric energy directly from chemical energy resulting from the oxidation-reduction reaction between the fuel gas and the oxidizer gas.
For fuel cell systems of this type, it is necessary to control the differential pressure (hereinafter referred to as the anode-cathode differential pressure) between a fuel gas supply pressure (gas supply pressure) on the fuel pole side and an oxidizer gas supply pressure (gas supply pressure) on the oxidizer pole side to a predetermined value or smaller in order to prevent possible damage to the electrolyte membrane and to allow the electrolyte membrane to last longer. To reduce the anode-cathode differential pressure, for example, Japanese Patent laid-Open No. 2003-068334 proposes a technique for varying a set pressure for a hydrogen regulator that adjusts the fuel gas supply pressure depending on the oxidizer gas supply pressure, determined by a fuel cell load (a generation requirement on the fuel cell).